Currently, an Optical Transport Network (OTN), as a core technology of a transport network, includes electrical and optical technical specifications, has abundant Operation, Administration and Maintenance (OAM), a strong Tandem Connection Monitoring (TCM) capability, and an out-of-band Forward Error Correction (FEC) capability, and can implement flexible scheduling of and management on high-capacity services.
With an increase in service traffic and diversified development of services, in comparison with an interface having a fixed rate provided by a conventional OTN, the industry is more inclined to provide an OTN interface having a multi-granularity level rate. Currently, the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) standards organization is formulating an Optical Channel Transport Unit-Cn (OTUCn) (C is the Roman numeral for 100, and n is a positive integer) interface for an application on a more than 100 Gbit/s OTN. The OTUCn interface provides a capability of processing an electrical interface having a rate of n*100 Gbit/s, and an OTUCn signal includes 20*n 5-Gbit/s timeslots.
A frame structure of an OTUCn frame defined in an OTUCn signal is shown in FIG. 1, the OTUCn frame includes n OTU subframes, and each OTU subframe has 4 rows and 3824 columns. A Frame Alignment Overhead (FA OH) is a frame alignment overhead byte, and provides a function of frame synchronization. An OTU OH is an OTUCn overhead byte, uses the OTUCn as a signal, manages and monitors the signal, and provides a network management function at a level of an optical channel transport unit. Majority of overhead information in OTUCn overheads is carried by using an OTU OH of an OTU subframe (OTU subframe #1) carried by a first lane, and remaining minority of overhead information is carried by using remaining OTU subframes carried by multiple lanes. The OTUCn frame is formed after the FA OH and OTUCn overheads are added to an Optical Channel Data Unit-Cn (ODUCn) frame. The ODUCn frame includes n ODU subframes, and each ODU subframe has 4 rows and 3824 columns. The ODUCn frame is formed after ODUCn overheads are added to an Optical Channel Payload Unit-Cn (OPUCn) frame. The OPUCn frame includes n OPU subframes, and each OPU subframe has 4 rows and 3810 columns. Each OPU subframe includes 2 columns of overhead areas and 3808 columns of payload areas, and each OPU subframe includes 20 5-Gbit/s timeslots, which are used to carry low-order services. Before the OTUCn frame is sent, single-byte or multi-byte interleaving processing is performed on the n OTU subframes of the OTUCn frame based on a type of a physical interface that is to be used for transmission, for example, single-byte or 16-byte interleaving processing is performed, to form a serial OTUCn bit data stream, and the serial OTUCn bit data stream is sent by using an optical module having a corresponding rate.
In a current system, an OTUCn interface provides a capability of processing an electrical interface having a rate of n*100 Gbit/s, and therefore can adapt to an optical module having a rate that is an integer multiple of 100 Gbit/s. Actually, in an actual application, optical modules whose rates, such as 150 Gbit/s and 250 Gbit/s, are not an integer multiple of 100 Gbit/s exist on a network. An OTUCn signal cannot adapt to an optical module whose rate is not an integer multiple of 100 Gbit/s. For example, in FIG. 2, when an OTU4 (having a rate of 100 Gbit/s) signal is sent or received by using an optical module having a rate of 150 Gbit/s, a problem of a waste of bandwidth exists; when an OTUC2 (having a rate of 200 Gbit/s) signal is sent or received by using an optical module having a rate of 150 Gbit/s, a problem that adaptation or transport cannot be performed exists. Therefore, in the current system, a problem that a rate of an OTN signal does not adapt to a rate of an optical module exists.